The Signal Acquisition Frontier: ECoG, Utah Arrays, and Neuropixels in BCI

The fidelity of a BCI is fundamentally constrained by its signal acquisition method. Electrocorticography, which places electrode grids on the surface of the dura mater, provides a middle-ground resolution, capturing local field potentials and high-frequency broadband activity from small populations of neurons. ECoG offers a superior signal-to-noise ratio and spatial resolution compared to non-invasive EEG, without the risks associated with penetrating the cortex, and is less susceptible to signal drift.

For the highest signal resolution, intracortical BCIs use microelectrode arrays like the Utah Array, which consists of 100 silicon-based microelectrodes arranged in a 10×10 grid. Each electrode tip records action potentials from one or a few nearby neurons. While this provides unparalleled access to the neural code, it induces a chronic foreign body response, leading to glial scarring and a gradual decline in signal quality and electrode yield over months to years due to the encapsulation of the array by reactive astrocytes and microglia.

The next generation of recording technology is exemplified by Neuropixels probes. These are complementary metal-oxide-semiconductor-based devices that pack nearly 1000 recording sites onto a single, slender shank. Their high channel count allows for simultaneous recording from hundreds to thousands of individual neurons across multiple cortical layers and even different brain structures, enabling the study of large-scale network dynamics that underlie complex behaviors.

A significant challenge with all implanted arrays is the biological integration, or lack thereof. The mechanical mismatch between rigid silicon probes and soft, pulsating brain tissue causes chronic inflammation and neuronal loss. Emerging solutions focus on flexible, polymer-based substrates like polyimide or parylene-C, which reduce the micromotions that drive the inflammatory response and promote better long-term stability.

Beyond the electrodes themselves, the sheer volume of data generated by high-channel-count probes presents a massive data transmission and power consumption challenge. Modern systems are moving towards on-probe amplification and multiplexing to reduce the number of physical wires exiting the skull. Fully implantable, wireless systems are now in development, which would drastically reduce the risk of infection and improve the quality of life for the user.

The future of BCI signal acquisition lies in “bio-integrative” electrodes—devices that are not just biocompatible but designed to form a functional interface with the neural tissue. This includes electrodes with surface coatings that release anti-inflammatory drugs, scaffolds that promote neuronal ingrowth, and even “neural lace” concepts involving injectable mesh electronics that interpenetrate the brain parenchyma with minimal disruption.